The research of phosphorus of Xiangxi River nearby the Three Gorges, China

The Xiangxi River is the first middling tributary of the Changjiang River near the Three Gorges Dam. The River is subject to phosphorus pollution mainly from industrial wastewater. As the water quality of the Xiangxi River could directly influence the water quality of the Three Gorges Reservoir, the research on phosphorus levels and its change in the sediment profile of the Xiangxi River could provide useful information in the dynamic changes in the system, thereby offering options for mitigative measures. Water and sediment samples from lower reaches of Xiangxi River were collected and the different forms of phosphorus in sediments of the Xiangxi River were studied. The concentrations of total phosphorus in sediment ranged from 757.67 to 1438.54 mg/kg. Inorganic phosphorus concentrations ranged from 684.63 to 1055.58 mg/kg. Phosphorus contamination was serious in some parts of the Xiangxi River. With an average concentration of 635.17 mg/kg, calcium-bound phosphorus is the main form among different inorganic phosphorus forms. Labile phosphorus and iron/aluminum-bound phosphorus measured 3.40, 0.05and 35.28 mg/kg, respectively. The mobilization potential of phosphorus of sediments was studied through adsorption and release experiments. The equilibrium concentration of phosphorus adsorption and release was around 0.1 mg/L. The initial concentrations of phosphorus in the overlying water and the sediments have obvious effect on phosphorus mobilization potential. In addition, the release rate of phosphorus in sediment increased with water depth.

Environmental signals: Synthetic humic substances act as xeno-estrogen and affect the thyroid system of Xenopus laevis

According to outdated paradigms humic substances (HS) are considered to be refractory or inert that do not directly interact with aquatic organisms. However, they are taken up and induce biotransformation activities and may act as hormone-like substances. In the present study, we tested whether HS can interfere with endocrine regulation in the amphibian Xenopus laevis. In order to exclude contamination with phyto-hormones, which may occur in environmental isolates, the artificial HS 1500 was applied. The in vivo results showed that HS 1500 causes significant estrogenic effects on X. laevis during its larval development and results of semi-quantitative RT-PCR revealed a marked increase of the estrogenic biomarker estrogen receptor mRNA (ER-mRNA). Furthermore, preliminary RT-PCR results showed that the thyroid-stimulating hormone (TSH beta-mRNA) is enhanced after exposure to HS1500, indicating a weak adverse effect on T3/T4 availability. Hence, HS may have estrogenic and anti-thyroidal effects on aquatic animals, and therefore may influence the structure of aquatic communities and they may be considered environmental signaling chemicals. (c) 2005 Elsevier Ltd. All rights reserved.

Ni silicide nanowires analysis by atom probe tomography

The Ni silicide formed at low temperature on Si nanowire has been analyzed by atom probe tomography (APT) thanks to a special technique for sample preparation. A method of preparation has been developed using the focused ion beam (FIB) for the APT analysis of nanowires (NWs). This method allow for the measurement of the radial distribution when a NW is cut, buried in a protective metal matrix, and finally mounted on the APT support post. This method was used for phosphorous doped Si NWs with or without a silicide shell, and allows obtaining the concentration and distribution of chemical elements in three-dimensions (3D) in the radial direction of the NWs. The distribution of atoms in the NWs has been measured including dopants and Au contamination. These measurements show that δ-Ni2Si phase is formed on Si NW, Au is found as cluster at the Ni/δ-Ni2Si interface and P is segregated at the δ-Ni2Si/ Si NW interface. The results obtained on NWs after silicidation were compared with the silicide on the Si substrate, showing that the same silicide phase δ-Ni2Si formed in both cases (NWs and substrate). © 2013 Elsevier B.V. All rights reserved.

Hydroxylated metabolites of polychlorinated biphenyls and their endocrine disrupting mechanism

Hydroxylated polychlorinated biphenyls (OH-PCBs a group of main active metabolites of polychlorinated biphenyl (PCBs) which are typical persistent organic pollutants (Pops) I have been identified in wild animals and human. The endocrine disruption of OH-PCBs has been drawn great attention due to the similarity of their chemical structures to the natural estrogens and thyroid hormones. The metabolic pathways of PCBs, the levels of OHPCBs in organism, the endocrine disruption and other adverse effects of OH-PCBs are reviewed. The further investigation of OH-PCBs will not only reveal the toxicological mechanism of PCBs, but also can lay scientific basis for setting up the risk assessment of POPs contamination and early-warning system in China.

Dynamics of microcystins-LR and -RR in the phytoplanktivorous silver carp in a sub-chronic toxicity experiment

A sub-chronic toxicity experiment was conducted to examine tissue distribution and depuration of two microcystins (microcystin-LR and microcystin -RR) in the phytoplanktivorous filter-feeding silver carp during a course of 80 days. Two large tanks (A, B) were used, and in Tank A, the fish were fed naturally with fresh Microcystis viridis cells (collected from a eutrophic pond) throughout the experiment, while in Tank B, the food of the fish were M. viridis cells for the first 40 days and then changed to artificial carp feed. High Performance Liquid Chromatography (HPLC) was used to measure MC-LR and MC-RR in the M. viridis cells, the seston, and the intestine, blood, liver and muscle tissue of silver carp at an interval of 20 days. MC-RR and MC-LR in the collected Microcystis cells varied between 268-580 and 110-292 mug g(-1) DW, respectively. In Tank A, MC-RR and MC-LR varied between 41.5-99.5 and 6.9-15.8 mug g(-1) DW in the seston, respectively. The maximum MC-RR in the blood, liver and muscle of the fish was 49.7, 17.8 and 1.77 mug g(-1) DW, respectively. No MC-LR was detectable in the muscle and blood samples of the silver carp in spite of the abundant presence of this toxin in the intestines (for the liver, there was only one case when a relatively minor quantity was detected). These findings contrast with previous experimental results on rainbow trout. Perhaps silver carp has a mechanism to degrade MC-LR actively and to inhibit MC-LR transportation across the intestines. The depuration of MC-RR concentrations occurred slowly than uptakes in blood, liver and muscle, and the depuration rate was in the order of blood > liver > muscle. The grazing ability of silver carp on toxic cyanobacteria suggests an applicability of using phytoplanktivorous fish to counteract cyanotoxin contamination in eutrophic waters. (C) 2003 Elsevier Ltd. All rights reserved.

Environmental threats to children's health in Southeast Asia and the Western Pacific

The Southeast Asia and Western Pacific regions contain half of the world's children and are among the most rapidly industrializing regions of the globe. Environmental threats to children's health are widespread and are multiplying as nations in the area undergo industrial development and pass through the epidemiologic transition. These environmental hazards range from traditional threats such as bacterial contamination of drinking water and wood smoke in poorly ventilated dwellings to more recently introduced chemical threats such as asbestos construction materials; arsenic in groundwater; methyl isocyanate in Bhopal, India; untreated manufacturing wastes released to landfills; chlorinated hydrocarbon and organophosphorous pesticides; and atmospheric lead emissions from the combustion of leaded gasoline. To address these problems, pediatricians, environmental health scientists, and public health workers throughout Southeast Asia and the Western Pacific have begun to build local and national research and prevention programs in children's environmental health. Successes have been achieved as a result of these efforts: A cost-effective system for producing safe drinking water at the village level has been devised in India; many nations have launched aggressive antismoking campaigns; and Thailand, the Philippines, India, and Pakistan have all begun to reduce their use of lead in gasoline, with resultant declines in children's blood lead levels. The International Conference on Environmental Threats to the Health of Children, held in Bangkok, Thailand, in March 2002, brought together more than 300 representatives from 35 countries and organizations to increase awareness on environmental health hazards affecting children in these regions and throughout the world. The conference, a direct result of the Environmental Threats to the Health of Children meeting held in Manila in April 2000, provided participants with the latest scientific data on children's vulnerability to environmental hazards and models for future policy and public health discussions on ways to improve children's health. The Bangkok Statement, a pledge resulting from the conference proceedings, is an important first step in creating a global alliance committed to developing active and innovative national and international networks to promote and protect children's environmental health.